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DESCRIPTION SSL provides endpoint Authentication and Communications Privacy over the Internet using Cryptography . In typical use, only the server is authenticated (i.e. its identity is ensured) while the client remains unauthenticated; mutual authentication requires Public Key Infrastructure (PKI) deployment to clients. The protocols allow Client/server applications to communicate in a way designed to prevent Eavesdropping , Tampering , and Message Forgery . SSL involves a number of basic phases:
During the first phase, the client and server negotiate which cryptographic algorithms will be used. Current implementations support the following choices:
HOW IT WORKS The SSL protocol exchanges records; each record can be optionally compressed, encrypted and packed with a Message Authentication Code (MAC). Each record has a ''content_type'' field that specifies which upper level protocol is being used. When the connection starts, the record level encapsulates another protocol, the handshake protocol, which has ''content_type'' 22. The client sends and receives several handshake structures:
TLS/SSL have a variety of security measures:
APPLICATIONS SSL runs on layers beneath application protocols such as HTTP , SMTP and NNTP and above the TCP or UDP transport protocol, which form part of the TCP/IP protocol suite. While it can add security to any protocol that uses reliable connections (such as TCP), it is most commonly used with HTTP to form HTTPS . HTTPS is used to secure World Wide Web pages for applications such as Electronic Commerce . It uses Public Key Certificate s to verify the identity of endpoints. While an increasing number of client and server products can support SSL natively, many still do not. In these cases, a user may wish to use standalone SSL products like Stunnel to provide encryption. However, the Internet Engineering Task Force recommended in 1997 that application protocols offer a way to upgrade to TLS from a plaintext connection, rather than use a separate port for encrypted communications - this prevents use of wrappers such as Stunnel. SSL can also be used to tunnel an entire network stack to create a VPN , as is the case with OpenVPN . HISTORY AND DEVELOPMENT Developed by Netscape , SSL version 3.0 was released in 1996 , which later served as a basis to develop TLS version 1.0, an IETF standard Protocol first defined in RFC 2246. Visa, MasterCard, American Express and many leading financial institutions have endorsed SSL for commerce over the Internet. SSL operates in modular fashion: its authors designed it for extendability, with support for forwards and backwards compatibility and negotiation between Peer s. Early weak keys Some early implementations of SSL could use a maximum of only 40-bit Symmetric Key s because of US government restrictions on the Export Of Cryptographic Technology . The US government explicitly imposed a 40-bit keyspace small enough to be broken by Brute-force Search by law enforcement agencies wishing to read the encrypted traffic, while still presenting obstacles to less-well-funded attackers. A similar limitation applied to Lotus Notes in export versions. After several years of public controversy, a series of lawsuits, and eventual US government recognition of changes in the market availability of 'better' cryptographic products produced outside the US, the authorities relaxed some aspects of the export restrictions. The 40-bit Key Size limitation has mostly gone away. Modern implementations use 128-bit (or longer) keys for symmetric key ciphers. Incorrect uses Some websites have been criticized for incorrectly using SSL and therefore negating the security benefits {Link without Title} . Such incorrect uses include:
This practice has been found present in many commercial websites such as those of Bank Of America and Washington Mutual {Link without Title} . STANDARDS The first definition of TLS appeared in RFC 2246: "The TLS Protocol Version 1.0". The current approved version is 1.1, which is specified in RFC 4346: "The Transport Layer Security (TLS) Protocol Version 1.1". Other RFC s subsequently extended TLS, including:
IMPLEMENTATION Programmers may use the OpenSSL or GnuTLS library for SSL / TLS functionality. Delphi programmers may use the library called Indy, which has ways of connecting components to an SSL intercept using the OpenSSL libraries. This enables the development of secure Web browsers and Web servers using Delphi/Indy/OpenSSL. The protocols supported are SSLv2 SSLv3 and TLS v1. TLS 1.1 As noted above, TLS 1.1 is the current approved version of the TLS protocol. TLS 1.1 clarifies some ambiguities and adds a number of recommendations. TLS 1.1 is very similar to TLS 1.0. The main reason for the new version number is a modified format for encrypted RSA pre-master secret, which is part of the client key-exchange message (if RSA is used), to use PKCS#1 v 2.1, as opposed to PKCS#1 v 1.5 in TLS 1.0. This is done to protect against an attack discovered by Daniel Bleichenbacher which can be launched against TLS 1.0 servers, using PKCS#1 v 1.5, which would fail in different ways depending if the decrypted format is correct or not. It also includes recommendations for avoiding remote timing attacks. A full list of differences between TLS 1.0 and TLS 1.1 is provided in RFC 4346 (Section 1.1). TLS 1.1 is currently supported by Opera and GnuTLS . SEE ALSO
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